EP0286215B1 - Electrically resistive tracks - Google Patents

Electrically resistive tracks Download PDF

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Publication number
EP0286215B1
EP0286215B1 EP88301518A EP88301518A EP0286215B1 EP 0286215 B1 EP0286215 B1 EP 0286215B1 EP 88301518 A EP88301518 A EP 88301518A EP 88301518 A EP88301518 A EP 88301518A EP 0286215 B1 EP0286215 B1 EP 0286215B1
Authority
EP
European Patent Office
Prior art keywords
track
substrate
heating element
metal
thick film
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP88301518A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0286215A1 (en
Inventor
Simon Balderson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thorn EMI PLC
Original Assignee
Thorn EMI PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thorn EMI PLC filed Critical Thorn EMI PLC
Priority to AT88301518T priority Critical patent/ATE72374T1/de
Publication of EP0286215A1 publication Critical patent/EP0286215A1/en
Application granted granted Critical
Publication of EP0286215B1 publication Critical patent/EP0286215B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
    • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
    • H05B3/748—Resistive heating elements, i.e. heating elements exposed to the air, e.g. coil wire heater
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/002—Heaters using a particular layout for the resistive material or resistive elements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/013—Heaters using resistive films or coatings
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/017—Manufacturing methods or apparatus for heaters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/07—Heating plates with temperature control means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49082—Resistor making
    • Y10T29/49085—Thermally variable

Definitions

  • This invention relates to heating elements comprising electrically resistive tracks intended to be formed on electrically insulative substrates, and it also relates to temperature sensors comprising such tracks.
  • heating devices including electric cooker hobs contain a heating element which, for a given setting, dissipates a constant power.
  • the heat-up rate of the element from ambient temperature to its normal operating temperature is accordingly limited by the constant power output at the maximum setting.
  • the inventor has realised that for such applications, there is an advantage in providing a heating element whose power dissipation varies with temperature.
  • a heating element comprising an electrically resistive track, said track consisting of a thick film having in the temperature range of from 0°C to 550°C a temperature coefficient of resistance in excess of 0.006 per degree C, said thick film including a metal and a glass in such proportions as to provide a suitable resistivity and a thermal expansion coefficient to match that of an electrically insulative substrate to which said track is to be applied and to permit adhesion of said track to a said substrate.
  • the extremely high temperature co-efficient of resistance of the heating element permits the track to have a low resistance at ambient temperatures, hence allowing, on energisation of the track, a high initial current to be drawn, thus achieving rapid initial heating.
  • This heating causes the resistance of the track to rise sharply, thus reducing the current as the normal operating temperature of the track is reached.
  • rapid heat-up and effective self-regulation are achieved.
  • Self-regulation also is achieved in the circumstance that the heating element has been pre-set to dissipate a given power and a pan of cold water (say) is placed directly over it (probably on top of a glass ceramic layer beneath which the heating element is mounted).
  • the pan will act as a heat sink, reducing the temperature of the element, thus causing it to draw more current and increasing the power dissipated by the element, and thus heat rapidly the contents of the pan.
  • a heating unit comprising an electrically insulative substrate, a heating element and a temperature sensor applied to said substrate; said sensor including an electrically resistive track, said track consisting of a thick film having in the temperature range of from 0°C to 550°C a temperature coefficient of resistance in excess of 0.006 per degree C, said thick film including a metal and a glass in such proportions as to provide a suitable resistivity and a thermal expansion coefficient to match that of said substrate and to permit adhesion of said track to said substrate.
  • the considerable variation in resistance of the sensor track with temperature is used to monitor the temperature of a substrate.
  • the printed format of the sensor track allows direct temperature monitoring of the surface of the substrate and avoids the problem of hysteresis associated with known temperature sensors, such as bimetal strips, which, because of their configuration, must necessarily be distant from the surface of the substrate.
  • Particularly useful materials for the track are nickel, iron and cobalt. It is also envisaged that alloys of these metals may be used, provided that the second phase of the alloy is insufficient to substantially reduce the temperature coefficient of resistance of the alloy from that of the bulk metal.
  • a thick film for a heating element has a composition by weight of 80% metal powder and 20% glass powder. Thick films having a composition by weight in the range of from 50% metal/50% glass to 95% metal/5% glass may also be used for the heating element.
  • a thick film for a temperature sensor on a heating unit has a composition by weight of 80% metal powder and 20% glass powder while in a second embodiment the composition by weight of the thick film is 50% metal powder to 50% glass powder.
  • the sensor track may also be made from a thick film having a composition by weight in the range of from 50% metal/50% glass to 95% metal/5% glass.
  • a typical, but non-limiting, glass powder used has the percentage composition by weight as below:
  • Figure 1 shows the approximate variation in resistance with temperature for a nickel thick film track having the composition by weight of 80% nickel and 20% glass.
  • the glass used was of the aforementioned composition. As can be seen, the variation in resistance with temperature is considerable.
  • the glass for the thick film track has a melting point of about 800°C. This enables the ink from which the track is to be made to be fired at a high temperature to ensure effective sintering of the metal without the glass bleeding out.
  • the high melting point of the glass also provides high temperature stability.
  • the composition of the glass is chosen so that the thermal expansion coefficient of the thick film is compatible with that of a substrate to which the track is to be applied.
  • the proportion of metal to glass in the thick film used affects, inter alia, the following properties:
  • Nickel and glass powders of average particle size 5 ⁇ m are mixed in the required ratio with a screen printing medium, such as ESL400, in a sufficient quantity to form a thick liquid slurry with a viscosity that allows the slurry to be easily screen printed.
  • the mixture is then passed through a triple roll mill to ensure adequate wetting of the nickel and glass powders by the screen printing medium, forming an ink.
  • the resulting ink is screen printed in the desired pattern onto the substrate, dried at 150°C and fired at a temperature in the range of from 750°C to 1100°C.
  • the firing procedure is preferably carried out in a nitrogen atmosphere to prevent oxidation of the metal.
  • a suitable pattern for the track is as shown in Figure 2 which shows a heating element 2 on a substrate 4, suitable for use as a hob unit.
  • the heating element 2 is connected to a power supply by electrical connectors (not shown).
  • a thick film track in accordance with this invention exhibits an ability to resist perforation even if a pore in the glass ceramic coating of the substrate and closely proximate to the track should rupture, for example as a result of the electric field established between the track, which generally is run at mains voltage, and the metallic support plate, which is generally earthed, or as a result of the heat generated where the track is used as a heavy duty heating element, for a cooker hob for example.
  • thick film tracks provided in accordance with this invention may advantageously be deposited upon substrates of the kind described in the parallel European patent application EP-A1-0 286216.
  • This patent application describes and claims a substrate for supporting electrical components, said substate comprising a plate member having on at least one surface a layer of a glass ceramic material wherein the percentage porosity of the glass ceramic layer, as defined hereinafter, is equal to or less than 2.5.
  • percentage porosity is meant the porosity at a random cross-sectional plane through the substrate perpendicular to the plate member expressed as the percentage ratio of the cross-sectional area of pores on the plane to the cross-sectional area of the remainder of the glass ceramic layer on that plane.
  • a heating element in accordance with the invention lends itself to use in conjunction with an energy management system, especially where two or more units are incorporated in a hob-top or cooker, thus permitting avoidance of the possibility that two or more elements could attempt to draw surge currents simultaneously.
  • the considerable variation in resistance of the track with temperature renders it possible to use the track or tracks included in a given system as part of a bridge circuit, for example, to monitor the current temperature of the or each track.
  • FIG. 3 shows (external connections not shown) a heating unit 10 comprising a substrate 11 bearing a heating element 12 and a temperature sensor 14, the temperature sensor being a thick film track having a high temperature coefficient of resistance as mentioned hereinbefore.
  • the heating element comprises a thick film track (for example, a heating element in accordance with said first aspect of the present invention)
  • the heating track and sensor track may be manufactured in the same process.
  • a sensor track could be arranged to closely follow the path of an associated heater track so as to cover a large area of the substrate.
  • An area to be heated could be monitored by several sensors in the area acting as one pan-size sensor.
  • the sensor track may also be used to regulate the temperature of the substrate and heating track using a suitable electrical circuit to compare the resistance of the sensor track with that of a variable resistor whose resistance is set to correspond to that of the required temperature.
  • FIG. 4 An example of an electrical circuit suitable for use with the sensor track is shown in Figure 4, where the resistance 20 is the resistance of the sensor track 14 and the variable resistor 22 is pre-set to a resistance corresponding to the required temperature.
  • the output of the comparator 32 switches polarity when the resistances of the sensor track and the variable resistor are the same, and accordingly when the sensor track and substrate are at the required temperature, and so can be used to switch the power supply to the heating element on the substrate when the required temperature has been reached.
  • a suitable electrical connector for making a connection to a thick film track has a cross-sectional area suitable for the required current carrying capacity and comprises a plurality of conductive fibres braided together, each of the fibres having a diameter, preferably in the range of from 30 ⁇ m to 300 ⁇ m, so as to provide sufficient stiffness to the connector and to permit adhesion of the connector to the thick film track.
  • the connector may be made of various metals, the most suitable metal for a particular application depending in part on the material of the thick film track to which the connector is to be adhered. Suitable metals include stainless steel, nickel and copper.
  • the connector is adhered to the track using a glass/metal adhesive, advantageously the same conductive ink as used to form the thick film track.
  • the whole is then overglazed using a protecting glass or glass ceramic overglaze to protect the thick film tracks and allow high temperature stable operation.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Surface Heating Bodies (AREA)
  • Resistance Heating (AREA)
  • Non-Adjustable Resistors (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Cable Accessories (AREA)
  • Amplifiers (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Electroluminescent Light Sources (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Led Device Packages (AREA)
  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
  • Electronic Switches (AREA)
  • Control Of Resistance Heating (AREA)
EP88301518A 1987-02-25 1988-02-23 Electrically resistive tracks Expired - Lifetime EP0286215B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88301518T ATE72374T1 (de) 1987-02-25 1988-02-23 Bahnen mit elektrischem widerstand.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB878704467A GB8704467D0 (en) 1987-02-25 1987-02-25 Electrically resistive tracks
GB8704467 1987-02-25

Publications (2)

Publication Number Publication Date
EP0286215A1 EP0286215A1 (en) 1988-10-12
EP0286215B1 true EP0286215B1 (en) 1992-01-29

Family

ID=10612950

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88301518A Expired - Lifetime EP0286215B1 (en) 1987-02-25 1988-02-23 Electrically resistive tracks

Country Status (15)

Country Link
US (1) US4859835A (fi)
EP (1) EP0286215B1 (fi)
JP (1) JPS63252380A (fi)
AT (1) ATE72374T1 (fi)
AU (1) AU600341B2 (fi)
CA (1) CA1291198C (fi)
DE (1) DE3868111D1 (fi)
DK (1) DK99688A (fi)
ES (1) ES2029008T3 (fi)
FI (1) FI87964C (fi)
GB (1) GB8704467D0 (fi)
GR (1) GR3003779T3 (fi)
IE (1) IE62355B1 (fi)
NO (1) NO880814L (fi)
NZ (1) NZ223611A (fi)

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GB8717035D0 (en) * 1987-07-18 1987-08-26 Emi Plc Thorn Thick film track material
JPH02129884A (ja) * 1988-11-08 1990-05-17 Nkk Corp 赤外線放射体
GB8905014D0 (en) * 1989-03-04 1989-04-19 Emi Plc Thorn Electrical connectors
JP2816339B2 (ja) * 1989-12-29 1998-10-27 東京エレクトロン株式会社 加熱装置
US5221829A (en) * 1990-10-15 1993-06-22 Shimon Yahav Domestic cooking apparatus
GB9024419D0 (en) * 1990-11-09 1991-01-02 Ist Lab Ltd Heating apparatus
JPH05198356A (ja) * 1991-02-26 1993-08-06 Lapin Demin Gmbh 平面発熱体及びその製造方法
GB2269980B (en) * 1992-08-13 1996-07-03 Ist Lab Ltd Apparatus for heating liquid
GB9302965D0 (en) * 1993-02-15 1993-03-31 Strix Ltd Immersion heaters
US5475199A (en) * 1993-12-22 1995-12-12 Buchanan; R. Craig Planar electric heater with enclosed U-shaped thick film heating element
AT408299B (de) * 1994-03-30 2001-10-25 Electrovac Heizvorrichtung für elektrische heizplatten, zündeinrichtungen, temperatursensoren od. dgl.
GB9423900D0 (en) * 1994-11-26 1995-01-11 Pifco Ltd Improvements to thick film elements
GB2296847B (en) * 1994-11-30 1999-03-24 Strix Ltd Electric heaters
JP3826961B2 (ja) * 1996-03-25 2006-09-27 ローム株式会社 加熱体およびその製造方法
WO1997039603A1 (en) 1996-04-18 1997-10-23 Strix Limited Electric heaters
DE19638832A1 (de) * 1996-09-21 1998-03-26 Ako Werke Gmbh & Co Heizleiter für ein Kochfeld
JP3983304B2 (ja) * 1997-05-29 2007-09-26 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ 加熱素子
US6117367A (en) * 1998-02-09 2000-09-12 International Business Machines Corporation Pastes for improved substrate dimensional control
DE10053415A1 (de) * 2000-10-27 2002-05-29 Bsh Bosch Siemens Hausgeraete Elektrischer Heizkörper
DE10065723A1 (de) * 2000-12-29 2002-07-04 Bosch Gmbh Robert Anordnung zur Temperaturmessung und -regelung
EP1395177B1 (en) * 2001-05-31 2006-07-19 Respironics Inc. Heater for optical gas sensor
US7301125B2 (en) * 2001-05-31 2007-11-27 Ric Investments, Llc Heater for optical gas sensor
US7106167B2 (en) * 2002-06-28 2006-09-12 Heetronix Stable high temperature sensor system with tungsten on AlN
DE60322649D1 (de) * 2002-11-06 2008-09-18 Mold Masters 2007 Ltd Heisskanaldüse mit flächigem Schichtheizelement
US7510392B2 (en) * 2002-11-06 2009-03-31 Mold-Masters (2007) Limited Injection nozzle with a removable heater device having one or more heating elements
FR2927233B1 (fr) * 2008-02-08 2011-11-11 Oreal Dispositif pour l'application d'un produit cosmetique, comportant un organe chauffant
PL2106194T3 (pl) * 2008-03-28 2014-05-30 Braun Gmbh Wkładka grzejna z regulacją temperatury
EP2106195B1 (en) * 2008-03-28 2010-05-05 Braun GmbH Heating element with temperature sensor
GB2466219A (en) * 2008-12-12 2010-06-16 Otter Controls Ltd Thick film heating element
GB2470368A (en) * 2009-05-19 2010-11-24 Sagentia Ltd A glass kettle with a heating element comprising a film coating of semiconducting material
EP2820915B1 (en) * 2012-02-27 2017-01-04 Watlow Electric Manufacturing Company Temperature detection and control system for layered heaters
KR20220027272A (ko) * 2016-04-07 2022-03-07 마테리온 코포레이션 산화 베릴륨 일체형 저항 히터
US11351331B2 (en) * 2017-12-08 2022-06-07 Fisher & Paykel Healthcare Limited Heater plate for respiratory humidification systems
KR102056084B1 (ko) 2018-08-21 2019-12-16 엘지전자 주식회사 전기 히터
KR102159802B1 (ko) * 2018-08-21 2020-09-25 엘지전자 주식회사 전기 히터
US11064738B2 (en) * 2020-10-20 2021-07-20 Dr. Dabber Inc. Ceramic heating element with embedded temperature sensor and electronic vaporizer having a ceramic heating element with embedded temperature sensor
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Also Published As

Publication number Publication date
CA1291198C (en) 1991-10-22
FI87964C (fi) 1993-03-10
FI880861A (fi) 1988-08-26
NZ223611A (en) 1990-07-26
IE880491L (en) 1988-08-25
FI880861A0 (fi) 1988-02-24
ES2029008T3 (es) 1992-07-16
GB8704467D0 (en) 1987-04-01
DK99688D0 (da) 1988-02-25
AU1210288A (en) 1988-09-01
FI87964B (fi) 1992-11-30
EP0286215A1 (en) 1988-10-12
DE3868111D1 (de) 1992-03-12
NO880814D0 (no) 1988-02-24
ATE72374T1 (de) 1992-02-15
DK99688A (da) 1988-08-26
NO880814L (no) 1988-08-26
AU600341B2 (en) 1990-08-09
GR3003779T3 (fi) 1993-03-16
US4859835A (en) 1989-08-22
IE62355B1 (en) 1995-01-25
JPS63252380A (ja) 1988-10-19

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